Referring to FIG. 1, a conventional Gilbert mixer includes a transconductance unit 12, a mixer unit 11, a first resistor (R11) and a second resistor (R12).
The trans conductance unit 12 receives a differential input voltage signal pair of intermediate frequency, and converts the differential input voltage signal pair into a differential input current signal pair.
The mixer unit 11 receives a differential oscillatory voltage signal pair, and is coupled to the trans conductance unit 12 for receiving the differential input current signal pair therefrom. The mixer unit 11 mixes the differential oscillatory voltage signal pair and the differential input current signal pair to generate a differential mixed current signal pair that includes a first mixed current signal (IRF1) and a second mixed current signal (IRF2) and that is of radio frequency.
The first resistor (R11) has a first terminal that receives a supply voltage (VDD1), and a second terminal that is coupled to the mixer unit 11 for receiving the first mixed current signal (IRF1) therefrom and that outputs a first mixed voltage signal (VRF1).
The second resistor (R12) has a first terminal that receives the supply voltage (VDD1), and a second terminal that is coupled to the mixer unit 11 for receiving the second mixed current signal (IRF2) therefrom and that outputs a second mixed voltage signal (VRF2). The first and second mixed voltage signals (VRF1, VRF2) constitute a differential mixed voltage signal pair.
When the conventional Gilbert mixer has a relatively high conversion gain, the first and second resistors (R11, R12) consume relatively high power. So, the conventional Gilbert mixer is unable to simultaneously achieve low power consumption and high conversion gain.